Cold lability of mouse sperm binding to zona pellucida

✍ Scribed by Heffner, Linda J. ;Storey, Bayard T.

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 560 KB
• Volume: 219
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402190204

✦ Synopsis

Abstract

Epididymal spermatozoa were maintained at 4°C during and after release from the epididymis to assess the effect of membrane fluidity on acquisition by the sperm of the ability to bind to zonae pellucidae of mouse eggs. The hypothesis to be tested was: If membrane fluidity is necessary for acquisition of the ability to bind, then exposure of sperm to 4°C to reduce fluidity markedly should lead to a characteristic delay time in acquiring the ability to bind to zonae. This result was not observed; instead, the relative extent of binding measured at 37°C was decreased relative to control by preincubation at 4°C. The relative extent of binding was reduced to 43% of control after 15 min and to 20% of control after a 60‐min preincubation at 4°C. The loss of binding ability was not reversed by subsequent exposure to 37°C in the insemination mixture for up to 60 min if fresh sperm were dispersed directly from epididymides into the cold medium. Dispersal of sperm into medium at 37°C followed by a 15‐min preincubation at this temperature, during which time sperm acquire the ability to bind to zonae, conferred full protection against cold‐induced loss of binding ability. This loss could not be attributed to motility effects: Mouse sperm are completely immotile if cooled to 4°C, but fully regain their original motility upon warming to 37°C, the temperature of the insemination medium. The binding sites on the sperm plasma membrane for the zona pellucida appear to lose irreversibly their binding ability at 4°C with a half‐time of about 15 min. These results suggest the hypothesis that rearrangement of binding site subunits is involved in the acquisition of the ability to bind to zonae, rather than long‐range interaction of plasma membrane proteins.